A browser helper object from McAfee, the Site Advisor integrates with your web browser and launches automatically. It contains a library of malicious websites and monitors your browsing to alert you or prevent you from visiting a malicious site. The Site Advisor plugin routinely communicates with the McAfee server to update its index of malicious sites. Based in Santa Clara, California, McAfee was founded in 1987. McAfee is best known for its McAfee Total Security protection suite and its various components.
If you want a detailed security rating about your SiteAdv.dll (and all other running background processes) read the following user opinions, and download the free trial version of Security Task Manager.

Note: Any malware can be named anything - so you should check where the files of the running processes are located on your disk.
If a "non-Microsoft" .exe file is located in the C:\Windows or C:\Windows\System32 folder, then there is a high risk for a virus, spyware, trojan or worm infection!
Check it out!